Download Amoxicillin - Mar Vista Animal Medical Center

Amoxicillin
AVAILABLE IN SUSPENSION &
50 mg, 100 mg, 200 mg, 400 mg
TABLETS
HISTORY AND BACKGROUND
Thanks to work by Alexander Fleming (1881-1955), Howard Florey ( 1898-1968) and Ernst Chain
(1906-1979), penicillin was first produced on a large scale for human use in 1943. At this time, the
development of a pill that could reliably kill bacteria was a remarkable development and many lives
were saved during World War II because this medication was available.
But quickly, it became obvious that this new "wonder drug" could bear improvement. For example:
• Penicillin is not well absorbed from the intestinal tract meaning that at least 70% of an oral dose is
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wasted.
Penicillin is also a short-acting medication, with half of the amount circulating being removed from
the body every half hour.
Not all bacteria have the type of cell wall which is susceptible to destruction by penicillin. (Bacteria
are classified as Gram negative or Gram positive, depending on the cell wall characteristics.
Penicillin is able to punch holes through the Gram positive cell wall but is not very effective
against the Gram negative cell wall.)
Staphylococci (an important group of bacteria) have developed an enzyme to break the penicillin
molecule apart and are thus rarely susceptible to penicillin.
Amoxicillin represents a synthetic improvement upon the original penicillin molecule. Amoxicillin is
better able to resist damage from stomach acid so less of an oral dose is wasted. While it is still
susceptible to destruction by staphylococcal enzymes, it does have a much broader spectrum against
the Gram negative cell wall and is able to last a bit longer.
USES OF THIS MEDICATION
Amoxicillin is regarded as having a fairly broad spectrum against many bacteria thus it is used both on
organisms known to be sensitive to it plus it is a good selection when the sensitivity of bacteria is
unknown. It is especially helpful in anaerobic infections (those which grow without the benefit of
oxygen). Typical uses might include:
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Infected bite wounds
Upper respiratory infections
Infected teeth
Bladder infections
It should be noted that staphylococcal infections are NOT sensitive to this medication with two
exceptions:
• Staph infections in the bladder are frequently sensitive to amoxicillin simply because the kidney
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concentrates such a large amount of amoxicillin in the bladder. The Staph enzymes are
overwhelmed by the huge concentration of antibiotic and the Staph organism is killed.
Staph infections are sensitive to amoxicillin if clavulanic acid is given concurrently to protect
amoxicillin from the Staph enzymes. (Amoxicillin/Clavulanic acid combinations are marketed
under the names Clavamox and Augmentin.)
In these two situations, amoxicillin should prevail over a Staph infection; however, recent times have
created yet another special situation: Methicillin-Resistant Staphylococci. These bacteria have mutated,
have less predictable sensitivity, and do not follow the above rules for Staph sensitivity.
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INTERACTIONS WITH OTHER DRUGS
When the organism in a serious infection cannot be isolated, a common strategy is to attempt to "cover"
for all possible bacteria. Amoxicillin is frequently used in combination with other antibiotics for this
purpose.
Clavulanic acid may be added to amoxicillin to increase amoxicillin's spectrum against staphylococcal
bacteria.
Amoxicillin is believed to synergize with members of the fluorquinolone class of antibiotics
(enrofloxacin, orbifloxacin etc.)
Concurrent use of amoxicillin with methotrexate (an agent of cancer chemotherapy) can increase the
toxicity of the methotrexate.
SIDE EFFECTS
Some individuals experience nausea with this medication. Giving the medication with food seems to
reduce this effect.
SPECIAL CAUTIONS
The oral suspension should be refrigerated, though if it is mistakenly left out of the refrigerator, this is
not a problem. The oral suspension should be discarded after 2 weeks.
Amoxicillin may be given with or without food.
Amoxicillin will cross the placenta in a pregnant patient but is felt to be safe for use during pregnancy.
The use of amoxicillin may cause some brands of urine dipsticks to falsely test positive for glucose.
Page last updated: 1/5/2017
Mar Vista Animal Medical Center
3850 Grand View Blvd., Los Angeles, CA 90066 l (310) 391-6741 l Fax: (310) 391-6744
Additional drug and general pet care information can be found on our world wide web site:
http://www.marvistavet.com